Corneal surgery apparatus and correction data determining methods

ABSTRACT

A corneal surgery apparatus for correcting a refractive error by ablating corneal tissue with a laser beam, which is capable of finding a pattern of correction optimum for a patient so as to ensure precise correction, and a method of determining correction data. The corneal surgery apparatus is provided with input means for inputting refractive power data on a contact lens used on a trial basis, calculation means for converting the refractive power data to obtain ablation data, control means for controlling an ablation amount of the corneal tissue based on the ablation data, storage means for storing the refractive power data in correspondence with each contact lens, and revising means for revising the refractive power data on the contact lens. The correction data determining method includes a process for obtaining a value of correction made with a contact lens based on a result of an ophthalmic examination, a process for selecting a contact lens for trial use based on the obtained values, and a process for converting the refractive power data on the selected contact lens into the ablation data for correcting the refractive error if the trial use of the contact lens bears a good result.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a corneal surgery apparatus forcorrecting a refractive error by ablating corneal tissue with a laserbeam and methods of determining data concerning the correction.

[0003] 2. Description of Related Art

[0004] Refractive errors of an eye include myopia, astigmatism,hyperopia, and presbyopia which makes it difficult to see things fromnear with aging. Conventionally, correction of presbyopia has beenconducted with eyeglasses, but contact lenses have also been used inrecent years. On the other hand, refractive corrections of myopia,astigmatism and hyperopia have been conducted with a corneal surgeryapparatus for changing a corneal shape with a laser beam as well as witheyeglasses and contact lenses. In the correction of presbyopia, however,patterns of the correction vary in accordance with patients' lifestyles. In corrective surgery with a laser beam, this variance makes itdifficult to correct presbyopia according to an optimum pattern ofcorrection desired by a patient. In addition, corrective surgery using alaser beam has a problem in that it is irreversible unlike thecorrection with eyeglasses or contact lenses.

SUMMARY OF THE INVENTION

[0005] The present invention has been made in view of the abovecircumstances and has an object to overcome the above problems and toprovide: 1) a corneal surgery apparatus capable of finding an optimumpattern of correction desired by a patient so as to ensure precisecorrection and 2) a method of determining data concerning thecorrection. In particular, the invention is to provide a corneal surgeryapparatus which may be applied to presbyopic correction and methods ofdetermining optimum correction data for correcting presbyopia with thecorneal surgery apparatus.

[0006] To achieve the objects and in accordance with the purpose of thepresent invention, as embodied and broadly described herein, a cornealsurgery apparatus for correcting a refractive error by ablating cornealtissue with a laser beam comprises: input means for inputting refractivepower data on a contact lens used on a trial basis; calculation meansfor converting the inputted refractive power data to obtain ablationdata; and control means for controlling an ablation amount of thecorneal tissue based on the obtained ablation data.

[0007] In another aspect of the present invention, a correction datadetermining method of correcting a refractive error by ablating cornealtissue comprises: a process in which a value of correction to be madewith a contact lens is obtained based on a result of an ophthalmicexamination; a process in which a contact lens for trial use is selectedbased on the obtained value of correction; and a process in whichrefractive power data on the selected contact lens is converted intoablation data for correcting the refractive error if the trial use ofthe contact lens bears a good result.

[0008] Further, in another aspect of the present invention, a cornealsurgery apparatus for correcting a refractive error by ablating cornealtissue with a laser beam comprises: an ablation unit which comprises alaser light source emitting a laser beam and an irradiation opticalsystem for irradiating the emitted laser beam onto a cornea; an inputunit which inputs refractive power data on a contact lens used on atrial basis; a calculation unit which converts the inputted refractivepower data to obtain ablation data; and a control unit which controlsthe ablation unit based on the obtained ablation data.

[0009] Additional objects and advantages of the invention are set forthin the following description, are obvious from the description, or maybe learned by practicing the invention. The objects and advantages ofthe invention may be realized and attained by means of instrumentalitiesand combinations particularly pointed out in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate embodiments of thepresent invention and, together with the description, serve to explainthe objects, advantages and principles of the invention. In thedrawings:

[0011]FIG. 1 is a view showing a schematic configuration of an opticalsystem and a control system of a corneal surgery apparatus as onepreferred embodiment according to the present invention;

[0012]FIG. 2 is a view showing intensity distribution of an excimerlaser beam applied to the corneal surgery apparatus shown in FIG. 1;

[0013]FIGS. 3A and 3B are views showing a schematic configuration of abeam restricting unit used in the corneal surgery apparatus shown inFIG. 1;

[0014]FIG. 4 shows an ablation pattern in an annular shape made by beamsoverlapping one another;

[0015]FIGS. 5A to 5E illustrate first and second patterns of presbyopiccorrection;

[0016]FIGS. 6A and 6B illustrate a third pattern of presbyopiccorrection;

[0017]FIG. 7 illustrates an ablation method in the third pattern ofpresbyopic correction with the beam restricting unit;

[0018]FIG. 8 is a flow chart depicting steps to correct presbyopia; and

[0019]FIG. 9 is a view showing an example of a screen for input ofrefractive power data appearing on a display of the corneal surgeryapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following detailed description of preferred embodimentsconsistent with the present invention will now be given referring to theaccompanying drawings.

[0021]FIG. 1 is a view showing a schematic configuration of an opticalsystem and a control system in a corneal surgery apparatus as one of thepreferred embodiments.

[0022] A laser light source 1 emits a laser beam, and in the presentembodiment, a laser light source which emits an excimer laser beam witha wavelength of 193 nm (preferably within 200 nm) may be used. Theexcimer laser beam emitted from the laser light source 1 is a pulsewave. Typically, the wave takes a shape of top hat distribution F(W) inwhich intensity distribution of a beam is approximately uniform in thehorizontal direction (the direction of the X axis), and it takes a shapeof the Gaussian distribution F(H) in the vertical direction (thedirection of the Y axis)(see FIG. 2).

[0023] The laser beam emitted from the laser light source 1 is deflected90 degrees by a plane mirror 2, and is then deflected again 90 degreesby a plane mirror 3. The mirror 3 may be moved by a driving unit 4 inthe vertical direction (the direction of the arrow) so as to shift thelaser beam parallel to the direction of the Gaussian distribution. Thisenables the laser beam to be displaced from an optical axis L of a beamdirecting optical system so as to ablate a subject evenly. For detaileddescription on this process, reference should be made to U.S. Pat. No.5,507,799 (Japanese Patent Unexamined Publication No. HEI 04-242644).

[0024] An image rotator 5 is rotationally driven on the optical axis Lby a driving unit 6 so as to rotate the laser beam around the opticalaxis L.

[0025] A changeable circular aperture 7 restricts an ablation zone to acircular shape, and an opening region of the aperture 7 is changed insize (in diameter) by a driving unit 8. A changeable slit aperture 9restricts an ablation zone to a slit shape. The slit aperture 9 ischanged in width and is rotated on the optical axis L by a driving unit10. The slit aperture 9 is used when correcting astigmatism.

[0026] A beam restricting unit 11 has an aperture 11 a of anapproximately semi-oval shape. FIG. 3A is a view of the restricting unit11 as viewed from the direction of the optical axis L, and FIG. 3B is aside elevation view of the unit 11. The aperture 11 a rotates 90 degreesabout an axis 11 b. When the aperture 11 a is positioned in broken linesas shown in FIG. 3B, the laser beam is transmitted except as obstructedby a shielding plate 11 c. On the other hand, while the aperture 11 a isrotating to a position indicated in solid lines, the laser beam isrestricted by the shape of the aperture 11 a. The restricting unit 11 isused when correcting presbyopia; otherwise it is removed from an opticalpath. A driving unit 12 comprises a driving part for inserting/removingthe restricting unit 11 in/from the optical path and for rotating theaperture 11 a and rotating a whole part of the restricting unit 11 aboutthe optical axis L.

[0027] A projecting lens 14 projects the circular aperture 7 and theslit aperture 9 on a cornea Ec of a patient's eye E. A dichroic mirror16 has a property of reflecting the excimer laser beam of 193 nm andtransmitting the visible light. The beam passed through the lens 14 isreflected by the dichroic mirror 16, and is then deflected 90 degrees tobe directed to the cornea Ec.

[0028] An observation optical system 17 has a binocular surgicalmicroscope. Description as to the binocular observation optical systemwill be omitted since it is commercially available and its configurationis not related to the present invention.

[0029] In surgery, the eye E is aligned to be brought into apredetermined positional relationship with the apparatus. In addition,the eye E is maintained in the aligned state by looking at anunillustrated fixation target. The alignment is performed by projectingslit images onto the eye E from at least two directions between whichthe optical axis of the observation optical system (an unillustratedobjective lens) is positioned, and positioning is then conducted basedon positional relationships between or among the slit images. Thisprocess is described in detail in U.S. Pat. No. 5,562,656 (JapanesePatent Unexamined Publication No. HEI 06-47001,) which may be referredto.

[0030] A computer 21 receives input of refractive power data and thelike concerning the patient's eye E to obtain control data for theapparatus. The computer 21 comprises a main body 21 a of the computerwith a program for obtaining ablation data and a database, a monitor 21b on which an input screen and inputted information are displayed, andan input control part 21 c consisting of a keyboard and a mouse. Thecontrol data obtained by the computer 21 are inputted to a controldevice 20 which controls operations of the laser light source 1 and eachof the driving units.

[0031] Brief description will now be given to ablation methods forcorrecting myopia, hyperopia and astigmatism in the aboveconfigurations.

[0032] For hyperopic correction, the opening region (diameter) of thecircular aperture 7 is fixed to restrict an ablation zone. The mirror 3is displaced from the optical axis L to deviate the laser beam, and theimage rotator 5 is rotated to shift the deviated laser beam so as tointerlock a chain of ablated spots. The pattern formed by interlockingthe ablated spots may be put into a nearly annular shape, as shown inFIG. 4, by selecting an appropriate combination of a rotationalfrequency of the image rotator 5 and a pulse repetition frequency of thelaser pulse. The number of irradiation pulses (irradiation time) isincreased as a deviation of the laser beam from the optical axis L isincreased by sequential movements of the mirror 3. This allows hyperopiato be corrected in such a manner that a central portion of a cornea isablated in lesser depth, and that a peripheral portion of the corneaablated is in greater depth. Diopters are controlled by changing a totalnumber of irradiation pulses, but without making any change in a ratioof the number of irradiation pulses for one position to that for anotherposition of the laser beam deviated from the optical axis L by themovements of the mirror 3. For more details on this process, referenceshould be made to U.S. Pat. No. 5,800,424 (Japanese Patent UnexaminedPublication HEI 08-66420).

[0033] Myopia may be corrected by two different methods. The firstmethod for myopic correction is as follows: the circular aperture 7restricts an ablation zone, the mirror 3 is sequentially moved to shiftthe laser beam in the direction of the Gaussian distribution, and theimage rotator 5 rotates the direction in which the laser beam is shiftedeach time the laser beam completes one zone by moving from one end tothe other end of the opening region of the circular aperture 7, therebycarrying out ablation in a uniformly circular shape as a whole. Theseoperations are repeated while the opening region (diameter) of thecircular aperture 7 is varied stepwise. This enables ablation to becarried out in the greatest depth on the corneal center, and in thelesser depth on the corneal periphery. For more details on this process,U.S. Pat. No. 5,637,109 (Japanese Patent Unexamined Publication No. HEI06-114083) is to be referred.

[0034] The second method for myopic correction is a method to which theablation for hyperopic correction is applied. By this method, a laserbeam is rotated in the neighborhood of the corneal center such thatablation is carried out in greater depth on the corneal center, and inlesser depth on the corneal periphery. Accordingly, myopia may becorrected by carrying out ablation while the position of the laser beamdeviated by the movements of the mirror 3 and the number of irradiationpulses are being controlled. As in the case of hyperopic correction,diopters may be controlled by changing the number of irradiation pulsesat each position of the laser beam.

[0035] Astigmatism may be corrected by enlarging the opening region(width) of the slit aperture 9 while the laser beam is shifted to carryout ablation as is the case with the first method for myopia correction.

[0036] Next, description will now be given to typical patterns ofpresbyopic correction profile and their corresponding methods ofablation. The description will be based on an assumption that myopiceyes are to be corrected.

[0037]FIGS. 5A to 5E illustrate first and second patterns of presbyopiccorrection. The first pattern of presbyopic correction is a correctionpattern in which a central correction zone 50 with its center positionedat a pupil and a peripheral correction zone 51 are used for near vision(eyesight from a short distance) and far vision (eyesight from a longdistance), respectively. On an outer circumference of the zone 51, anunillustrated transition zone (TZ) is formed which smoothly connects anablation zone and a non-ablation zone. The zone ranging from the pupilcenter to the zone 51 is an optical zone (OZ) which is opticallyinfluential.

[0038] In this pattern, the zone 50 for near vision is corrected by anamount of additional diopters in relation to the zone 51 for far vision.The method for this case varies depending on whether a value of myopiccorrection diopters S plus additional diopters ADD is negative orpositive. In the case of S+ADD=0D, the zone 50 is ablated uniformly notto have any influence on refractive power (not to make any change inshape).

[0039] When the value of myopic correction diopters S plus additionaldiopters ADD is negative, for example, with the myopic correctiondiopters S=−3D and ADD=2D, the opening region (diameter)of the circularaperture 7 is controlled to ablate the zone 50 to correct myopia by aremaining amount of the myopic correction diopters S=−1D. Subsequently,while the opening region (diameter) of the circular aperture 7, whichhas become as large as the size of the zone 50, is gradually widened,the zone 51 is ablated to correct myopia by an amount of the myopiccorrection diopters S=−3D (see FIG. 5B).

[0040] When the value of myopic correction diopters S plus additionaldiopters ADD is positive, for example, with the myopic correctiondiopters S=−1D and ADD=2D, the zone 50 is corrected by the amount ofS=+1D. In this case, while the zone 50 is ablated to correct hyperopiaby an amount of S=+1D, the zone 51 is also ablated to correct myopia bythe amount of the myopic correction diopters S=−1D using the secondmethod for myopic correction to which the ablation for hyperopiccorrection is applied (see FIG. 5C).

[0041] The second pattern of presbyopic correction is reverse to thefirst pattern of presbyopic correction; it is a correction pattern inwhich the zones 50 and 51 shown in FIG. 5A are used for far vision andnear vision, respectively. In the second pattern of presbyopiccorrection, the method also varies depending on whether the value ofmyopic correction diopters S plus additional diopters ADD is negative orpositive. In the case of S+ADD=0D, the zone 51 is not ablated, or isablated uniformly.

[0042] When the value of myopic correction diopters S plus additionaldiopters ADD is negative, for example, in the case of the myopiccorrection diopters S=−3D and ADD=2D, the opening region (diameter) ofthe circular aperture 7 is controlled to ablate the zone 50 to correctmyopia by the amount of the myopic correction diopters S=−3D, and thenthe zone 51 is also ablated to correct myopia by the remaining amount ofthe myopic correction diopters S=−1D (see FIG. 5D).

[0043] When the value of myopic correction diopters S plus additionaldiopters ADD is positive, for example, in the case of the myopiccorrection diopters S=−1D and ADD=2D, the zone 50 is ablated to correctmyopia by the amount of S=−1D. Thereafter, the zone 51 is ablated tocorrect hyperopia by the amount of S=+1D (see FIG. 5E).

[0044] Incidentally, in any case of the above patterns, it may bepreferred that a graduated zone having a continuously varying dioptricpower should be provided between the zones 50 and 51. This may beachieved during a transition from the zone 50 to the zone 51 in such amanner that diopters are changed by carrying out ablation to correctmyopia under the method by which the opening region (diameter) ofcircular aperture 7 is controlled or under the second method for myopiccorrection.

[0045]FIGS. 6A and 6B illustrates a third pattern of presbyopiccorrection. In this pattern, as shown in FIG. 6A, an upper correctionzone 60 in a semicircular shape is used for far vision, and a lowercorrection zone 61 which is a section enclosed by a circle 7′ and asemicircle 11 a′ is used for near vision. A zone 62 is a transition zonesmoothly connecting the zones 60 and 61.

[0046] In the third pattern, to begin with, the opening region(diameter) of the circular aperture 7 is controlled to ablate the insideof the optical zone including the zones 60 and 61 so as to correctmyopia by an amount of myopic correction diopters for far vision. Afterthat, the zone 61 is ablated in the following manner: the restrictingunit 11 is inserted into the optical path so as to arrange the shieldingplate 11 c to shield the zone 60 as shown in FIG. 7; ablation is carriedout to correct hyperopia by an amount of additional diopters with theopening region (diameter) of the circular aperture 7 kept in the samesize as the optical zone, while the aperture 11 a is gradually tiltedfrom a position parallel to the optical axis until the aperture 11 abecomes perpendicular to the optical axis; and this leads to ablate thezone 61 which is the section enclosed by the circle 7′ (a passage zoneof the circular aperture 7) and the semicircle 11 a′ (a passage zone ofthe aperture 11 a) by an amount of the additional diopters (see FIG.6B). During this ablation, tilting the aperture 11 a gradually forms thezone 62.

[0047] The third pattern of presbyopic correction may be modified invarious forms. For example, reversing a vertical relationship betweenpositions of the zones 60 and 61 may make it possible to use the upperand the lower zones for near and far vision correction, respectively.This may be achieved by rotating the restricting unit 11 about theoptical axis L. In addition, placement of both the zones may be changedwithout restraint; it does not have to be vertical, and may behorizontal where appropriate. Further, both the zones 60 and 61 may bechanged in size by moving the restricting unit 11 and thereby shifting aposition to place the aperture 11 a.

[0048] As described above, the typical patterns of presbyopic correctionhave been disclosed, and it may be possible to follow a pattern oftrifocal correction or to make a correction in a combination of some ofthe patterns mentioned above.

[0049] Additionally, the beam directing optical system for directing alaser beam to a patient's eye is not limited to the one disclosed in thepresent embodiment and its mode may come in various types. As describedin U.S. Pat. No. 5,906,608 (Japanese Patent Unexamined Publication No.HEI 09-266925), for instance, it may be possible to employ a mode inwhich the laser beam shaped like a rectangle is split with a mask forselectively dividing a longitudinal direction of the beam, so that aposition to project the beam onto a cornea may be shifted by themovement of the mirror 3 and the rotation of the image rotator 5.Alternatively, it may be also possible to employ a mode in which agalvano-mirror or the like is used for a two-dimensional scanning with asmall-spot beam shaped within 1 mm, so that a position to project thesmall-spot beam may be shifted. With a beam directing optical system inthese modes, ablation may be carried out in an arbitrary pattern ofshape by controlling the irradiation time at each position of the beam.

[0050] Next, steps to correct presbyopia with the present apparatus willnow be described with reference to FIG. 8.

[0051] First, an ophthalmic examination such as a basic examination ofcorneal shapes or refractive powers is conducted to obtain aprescription of diopters for far and near vision corrections.Conventionally, refractive power data are determined at this stage andsurgery is then performed. According to the present embodiment, however,prior to a keratorefractive surgery (corrective surgery) using a laserbeam, a soft contact lens (hereinafter, referred to as CL) is used as atrial lens to confirm optimum correction pattern and correctivediopters. Based on a result thus confirmed, corrective surgery is thenperformed with a laser beam.

[0052] In advance of putting a CL on the eye E for trial use, it isrequired to prepare many different types of CLs that have their owncorrection profiles created in association with the correction patternsavailable with the above-stated corneal surgery apparatus. Manufactureof CLs may be conducted by a CL maker, based on data about thecorrection patterns stored in the apparatus, or it may also be possibleto irradiate a beam on a CL having no dioptric power so that the CL maychange in shape.

[0053] After the basic ophthalmic examination, an operator checks up ona patient's background of eyesight and life style, and selects acorrection pattern, corrective diopters and the like for the patient.The operator makes the patient wear the selected CL on a trial basis,and observes a progress of any improvements achieved with the CL in thepatient's vision for a while. For example, in the above-mentioned firstto third patterns of presbyopic correction, the operator gives a test ondifferent CLs with their far and near vision zones varied in size, fromwhich he determines an optimum CL. He also confirms an optimum selectionof corrective diopters for far vision and near vision each by making atest on several CLs. This process may put a patient through a simulationof the improvements in his vision that will be achieved through cornealsurgery using a laser beam.

[0054] After the optimums for the patient is determined based on theprogress observation, the computer 21 of the apparatus may receive aninput of pre-operative corneal shape data and refractive power data(which may be called data on distribution of refractive powers as well)including a correction pattern of the selected CL, the size of theoptical zone, and both positions of and corrective diopters for the farand near vision zones each. FIG. 9 is an example of an input screen forthe refractive power data shown on the display 21 b. Data to be enteredin each entry field on the right side of the display come with theselected CL. The data may be, for example, attached to a packing caseand the like of the CL when the CL is manufactured, or the data may befurnished in a CL record book. This allows an operator to see the dataand input them from the input control part 21 c. Nevertheless, manualinput is so troublesome and prone to invite a mistake that the followingmethod may be practicable for input of the data.

[0055] Each of the packing cases and the like of a CL is provided with arecord number for identification of CLs. The refractive power data onCLs associated with the record numbers of the CLs are stored beforehandin a database possessed in the computer 21. It may also be possible thatthe data on the CLs manufactured by a CL maker is stored in a CD-ROM tobe incorporated into the computer 21 in advance. When the record numberof the selected CL is entered in a CL Number entry field 70 shown inFIG. 9, the refractive power data concerning the CL may be retrievedfrom the database to be inputted. Alternatively, the refractive powerdata on the CLs may be stored in a bar-code form (or, as two-dimensionalcodes if the data come in large quantity), and may be then attached tothe packing cases and the like of the CLs, so that the data may be readwith a bar code reader to be inputted.

[0056] It should be noted that, if the trial use of the CL contributesto accurate diagnosis of refractive power data on a patient, therefractive power data on the CL are inputted, and then a value for adata item may be corrected as needed using the input control part 21 c.

[0057] On the input screen shown in FIG. 9, a color map 75 of correctionpatterns is displayed graphically. The near and far vision zones areboth expressed in color in accordance with the corrective diopters. Anouter zone 76 on the color map 75 represents a transition zone. Thegraphic display of the color map 75 facilitates visible recognition ofcorrection patterns and verification of the data inputted incorrespondence with the CL selection.

[0058] Upon completion of inputting the pre-operative corneal shape dataand the refractive power data, the main body of the computer 21aconverts the refractive power data into the ablation data (data ondistribution of ablation). Based on the ablation data, the control datafor ablation are obtained according to the above-mentioned patterns, andare then transmitted to the control device 20. At the time of surgery,the operator observes the eye E through the observation optical system17 to perform alignment of the beam directing optical system, and theninputs laser irradiation commencement signals to the control device 20using a laser irradiation switch. The control device 20 controls thelaser light source 1 and the driving units to irradiate a laser beam sothat ablation may be carried out in any of the above-described manners.

[0059] Having fully been described, the present invention is intended tofind correction data optimum for each patient so as to ensure precisecorrection made with a laser beam.

[0060] The foregoing description of the preferred embodiments of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and modifications andvariations are possible in the light of the above teachings or may beacquired from practice of the invention. The embodiments chosen anddescribed in order to explain the principles of the invention and itspractical application to enable one skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto, and theirequivalents.

What is claimed is:
 1. A corneal surgery apparatus for correcting arefractive error by ablating corneal tissue with a laser beamcomprising: (a) input means for inputting refractive power data on acontact lens used on a trial basis; (b) calculation means for convertingthe inputted refractive power data to obtain ablation data; and (c)control means for controlling an ablation amount of the corneal tissuebased on the obtained ablation data.
 2. A corneal surgery apparatusaccording to claim 1, further comprising storage means for storing therefractive power data in correspondence with each contact lens, whereinthe input means comprises means for inputting an identifier assigned tothe contact lens and means for retrieving the refractive power datastored in the storage means with reference to the inputted identifier.3. A corneal surgery apparatus according to claim 1, further comprisingrevising means for revising the inputted refractive power data on thecontact lens, wherein the calculation means obtain the ablation databased on the revised data.
 4. A corneal surgery apparatus according toclaim 1, wherein: the contact lens includes a contact lens forpresbyopic correction; and the refractive power data includes data on afar vision zone, a refractive power on the far vision zone, a nearvision zone, and a refractive power on the near vision zone.
 5. Acorneal surgery apparatus according to claim 4, further comprisingdisplay means for graphically displaying the inputted data on the farvision zone and the near vision zone.
 6. A correction data determiningmethod of correcting a refractive error by ablating corneal tissuecomprising: (a) a process in which a value of correction to be made witha contact lens is obtained based on a result of an ophthalmicexamination; (b) a process in which a contact lens for trial use isselected based on the obtained value of correction; and (c) a process inwhich refractive power data of the selected contact lens are convertedinto ablation data for correcting the refractive error if the trial useof the contact lens bears a good result.
 7. A correction datadetermining method according to claim 6, wherein the contact lensincludes a lens geared for a correction pattern in which ablation iscarried out with a corneal surgery apparatus for ablating cornealtissue.
 8. A corneal surgery apparatus for correcting a refractive errorby ablating corneal tissue with a laser beam comprising: (a) an ablationunit which comprises a laser light source emitting a laser beam and anirradiation optical system for irradiating the emitted laser beam onto acornea; (b) an input unit which inputs refractive power data of acontact lens used on a trial basis; (c) a calculation unit whichconverts the inputted refractive power data to obtain ablation data; and(d) a control unit which controls the ablation unit based on theobtained ablation data.
 9. A corneal surgery apparatus according toclaim 8, wherein the irradiation optical system includes a circularaperture of which opening diameter is changeable, a projecting lenswhich projects the aperture onto the cornea, a shifting unit whichdisplaces a region to be irradiated with the laser beam from a center ofan optical zone on the cornea, and a rotator which rotates the laserbeam.
 10. A corneal surgery apparatus according to claim 9, wherein theirradiation optical system includes a beam restricting unit insertablein and removable from an optical path of the laser beam, the beamrestricting unit having a semi-oval aperture which is tilted to avariable angle with respect to an optical axis of the irradiationoptical system.